It's a scam, of course. The goal is to extort a "fine" of $100 to $200, purportedly to be paid to the U.S. Department of Justice. Send it as a MoneyPak order, you're told, and your computer will be unlocked.

If you pay, you may receive a 10-digit password that allows you to unfreeze your computer. Or you may get nothing, or demands for more payoffs to the people who are holding your computer hostage. That's why the virus is called "ransomware."

It may continue to capture personal information such as your user names, passwords and credit card numbers, and send them to the scammers. IC3 reports getting dozens of complaints a day about the ransomware scam.

Known as Reveton, the virus is a variant of the Citadel malware that cybercrooks use to hijack online banking accounts. If you suspect you've been hit, the FBI advises you to hire a professional to check your computer. You should also file a complaint on the IC3 website.

Like other malware, Reveton is usually installed on your computer when you open a malicious attachment, click on a link in an email or instant message, or visit scammer websites that promise such things as enticing videos or free prizes.

• Do the obvious: Don't open spam or emails from people you don't know. Don't visit sketchy websites.

• Make sure your operating system's automatic updating feature is turned on so you'll get the latest security protection. Windows users should download the free Microsoft Security Essentials. Macs are less vulnerable to ransomware, but Apple encourages Mac users with ransomware concerns to contact its support team.